The invention relates to a gas bag module.
Known gas bag modules comprise a gas bag with a gas bag wall which has a front and a rear wall section, an indentation running from the front wall section in the inflated state in the direction toward the rear wall section, which indentation is formed in that a part of the gas bag wall is prevented from an unimpeded movement towards outside of the module on unfolding of the gas bag. Such gas bags are intended to be incorporated in the steering wheel or the instrument panel and to protect the occupant in a frontal impact. The gas bag has an annular chamber which is to be inflated, and the inner wall, delimiting the indentation, is formed by the indentation. The indentation extends from the front wall centrally towards the rear, and the lowest point of the indentation is formed by a fabric piece which is permanently fastened to the gas bag module and hence on unfolding is not moved freely towards the occupant, to prevent him from being held back. The gas bag usually emerges obliquely outwards from the module owing to the annular shape of the chamber, and only subsequently does the front wall section move towards the occupant.
With an occupant sitting centrally and with a high impact intensity, it is to be prevented that the occupant""s head can plunge into the indentation. This is achieved by constructional approaches that are differingly complicated. The invention provides a simple, cost-effective solution for this.
This is achieved in a gas bag module which comprises a gas bag including at least one chamber as well as including a gas bag wall which has a front and a rear wall section. The gas bag further comprises an indentation running from the front wall section in an inflated state in a direction toward the rear wall section. The indentation is formed in that a part of the gas bag wall is prevented from an unimpeded movement towards outside of the module on unfolding of the gas bag. The gas bag, in a region of a mouth of the indentation, has a bubble-like inflatable extension in flow connection with the at least one chamber of the gas bag, which extension closes the indentation.
According to the preferred embodiment, the gas bag according to the invention has an indentation which at least in sections runs obliquely, which indentation is preferably already closed at its mouth and thus prevents the slightest plunging of the occupant""s head into the indentation. The obliquely running wall section makes it possible that, at least in the case of a heavy occupant plunging in the gas bag, the extension is supported by the gas bag wall defining the indentation. If applicable, such supporting is already provided in the fully inflated state of the gas bag, without an occupant acting. The inflatable extension may impart an asymmetric shape to the gas bag, and may compress the mouth laterally from one side and close it.
Preferably, the extension moves on inflation radially towards the mouth, in order to close it and to give the indentation an oblique orientation. The oblique orientation, however, is not necessarily to be created by the extension. The oblique orientation can be achieved by a middle axis of the indentation running obliquely with respect to the middle axis of the gas bag or by a part of the gas bag wall defining the indentation extending at least partially obliquely so that the indentation has not a fully cylindrical shape.
In the inflated state, the extension preferably projects outwards with respect to the front wall section, which is useful for the stability of the gas bag and also gives the extension, which acts like a closure, a greater stability.
The preferred embodiment of the gas bag makes provision that, in relation to the spread-out, non-inflated state of the gas bag, the latter consists of at least four fabric sections lying one over the other and being connected with each other. An upper and a lower fabric piece are provided to form the front and rear wall sections, respectively. In addition, the gas bag has two inner fabric pieces which delimit the indentation. These inner fabric pieces may have an asymmetrical annular shape and a bulge to form the extension. The inner fabric pieces are usually sewn to each other at their outer edges.
In one embodiment, provision can be made in addition that all the fabric pieces have a central opening, with the possibility of arranging the openings so as to be concentrical to each other, again in relation to the spread-out, non-inflated state of the gas bag.
The inner fabric pieces may have an identical external geometry, which facilitates the sewing of the two fabric pieces on the outer edge.
The bulges of the inner fabric pieces preferably have a shape which is similar to a mushroom cap. A ring segment then adjoins the underside of the cap.